You may have heard of British neurologist Oliver Sacks’ book The Man Who Mistook His Wife For A Hat.
At the heart of that story was a disease called prosopagnosia, or as it’s more commonly called, face blindness. A person with face blindness can no longer process the visual information that allows them to recognize a face.
The head remains but instead of it revealing itself as eyes, ears, nose and mouth, it becomes a scrambled puzzle.
Strikingly, they tend to be unaware of the problem. Often times persons with prosopagnosia are able to tell people apart due to hairdos or exaggerated features such as a big nose or ears. In these individuals’ worlds faces—and in most instances objects in general—are like scrambled, unsolvable visual puzzles.
So what causes this?
Our experience of the world tends to be seamless. For the most part we go about our days without noticing the strange quirks of our consciousness. As an example, we hardly pay attention to our breathing or heartbeat, the clothes touching our skin, or the blind spot in each one of our eyes.
That’s right—the area of your eye where your optic nerve is attached to your retina is devoid of sensory cells, leading to a blind spot. Don’t worry. Information from your other eye compensates for it as the visual information is processed in your brain.
But here we have what is clearly a missing area of our visual field that we hardly ever notice. Damage to the eyes obviously leads to blindness, but damage to later areas of the brain can lead to profound effects on one’s conscious experience of the world.